Let's see...
[ ] A long journey that ended in failure, but taught the greatest lesson of all to a hard working King. Hmm, possibly caster gil? able to beamspam using staffs.
[ ] A woman of astonishing beauty serving as a courtesan during the Sheng Dynasty. <Not sure here, chinese caster?
[ ] A lady brought forth as a unison between a Goddess and a Legendary Spear User. <scath skadi, runes and gaebolgs ahoy, also crystal magic, depending on if she gets lost belt king status, powerful
[ ] A man who led a destined king to his fate. <probably merlin. May or may not come with excalibur, bites his tongue when chanting, pretty powerful fae and buffing magic. Not the best outright fighter.
[X] A lady brought forth as a unison between a Goddess and a Legendary Spear User. <scath skadi, runes and gaebolgs ahoy, also crystal magic, depending on if she gets lost belt king status, powerful
Scath skadi would be my choice, runes are broken in the nasuverse. Should come with some level of martial prowess.
[ ] A total sadist engrossed in sadism, seeking to perform atrocities and misdeeds upon all enemies who catch his eye.
[ ] A man who completed tasks beyond mortal comprehension, going beyond the limits of humanity to become a monsterous powerhouse. <Could be herk, not sure since he started a demigod.
[ ] A Lawman who went through his life, bringing order and justice to everything in his homeland, akin to a Demon.
[] A Warrior who lost their path on the search for forgiveness from thier Leader, forever losing their mind over never being able to regain their honour. <possibly lancelot
Less sure on who to pick for zerker...but if the last one is lancelot, then scath skadi lancelot could be a powerful combination, since eternal arms mastery means all of our skill carries over into when we're under madness.
edit:
[X] A man who completed tasks beyond mortal comprehension, going beyond the limits of humanity to become a monsterous powerhouse. <Could be herk, not sure since he started a demigod.
see herk, pick herk, if you want a zerker you either go him or someone with arms mastery. I think the synergy with skadi could be found pretty easily, and divinity will more than likely stack in some way.